The present disclosure relates to a fixing device fixing a toner image on a sheet and an image forming apparatus including the fixing device.
An image forming apparatus is provided with a fixing device which heats and presses a toner image transferred on a sheet and fixes the toner image on the sheet. The fixing device includes a rotatable heating member heated by a heat source and a pressing member being pressed against the heating member to form a pressing area between the heating member and the pressing member. When the sheet on which the toner image is transferred passes through the pressing area, the toner image is heated and pressed to be fixed on the sheet. The fixing device further includes a separating member which comes into contact with the heating member and separates the sheet passed through the pressing area from the heating member.
Because the separating member comes into contact with the heating member, a fine offset toner adhered on a surface of the heating member is fused on the separating member, and then the heating member is scraped by the fused toner of the separating member. If a depth of the scraped portion increases, an image having white streak may be printed before the end of the lifetime of the fixing device. Against the problem, when a contact pressure between the separating member and the heating member is decreased, a separating failure for a specific sheet may occur. Alternatively, when the separating member reciprocates in an axis direction of the heating member to distribute the contact position between the separating member and the heating member, although some degree of effect can be obtained, it is difficult to keep the effect until the end of the lifetime of the fixing device.
Alternatively, a hard intermediate layer may be sometimes provided between a release layer and a primer layer of the heating member along a circumferential direction of the heating member. In addition, a cleaning member may be provided, which comes into contact with the non-contact portion where the separating claw (the separating member) does not come into contact with the heating member and collects the adhered substance produced by the fine offset toner.
However, when the intermediate layer is provided, the producing process for the heating member becomes complicate. In addition, the intermediate layer does not offer the effect for decreasing the abrasion of the release layer. When the cleaning member is provided, because it is required to add a new member, a cost may be increased and a control process for the cleaning member may be complicate. In addition, the cleaning performance may be decreased before the end of the lifetime of the fixing device.